#define _CRT_SECURE_NO_WARNINGS 1
/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* reverseList(ListNode* head)
    {
        ListNode* sent = new ListNode;
        ListNode* cur = head;
        while (cur != nullptr)
        {
            ListNode* tmp = cur;
            cur = cur->next;
            tmp->next = sent->next;
            sent->next = tmp;
        }
        return sent->next;
    }
};